This invention relates to a vacuum toilet system.
Vacuum toilet systems have been known for many years. The modern vacuum toilet system comprises a waste-receiving bowl, a sewer pipe that can be placed under a pressure that is substantially lower than that in the interior of the waste-receiving bowl, and a discharge valve for controlling passage of material from the waste-receiving bowl into the sewer pipe. A rinse liquid outlet is provided near the rim of the waste-receiving bowl and is connected through a rinse liquid valve to a source of pressurized rinse liquid. During a flush cycle, in which the discharge valve is opened, the rinse liquid valve is opened and rinse liquid is introduced into the waste-receiving bowl.
Non-recirculating vacuum toilet systems using plain water as a rinse liquid are attractive for use in aircraft. In such a system, it is conventional for the rinse liquid to be provided from the aircraft's potable water system. The potable water system includes a tank, pipes connecting the tank to consuming devices, such as the vacuum toilets and hand basins, and a pump for maintaining the water in the pipes under pressure.
An aircraft toilet system comprises a holding tank for receiving waste material from the waste-receiving bowl. In order to avoid transporting material that could be discharged from the aircraft in flight, gray water, i.e., water that, though not potable, can be discharged into the environment without treatment, e.g. water from hand basins and from galley sinks, is not fed into the vacuum toilet system so that it enters the holding tank but is discharged from the aircraft through a drain mast.
U.S. Pat. No. 4,713,847 issued Dec. 22, 1987, the disclosure of which is hereby incorporated by reference herein, discloses a vacuum toilet system in which a pump is used to deliver rinse water to a toilet bowl under control of a valve that is opened in response to actuation of a flush switch.
It has been proposed that an aircraft vacuum toilet system should employ gray water as the rinse liquid for the vacuum toilets. According to this proposal, which, as far as the applicants are aware, has not been reduced to practice, a reservoir for collecting gray water would be provided, and each toilet would be provided with means for drawing gray water from the reservoir and delivering it to the toilet in response to actuation of a flush switch.